Severe Idiopathic Constipation Is Associated With a Distinctive Abnormality of the Colonic Myenteric Plexus

GASTROENTEROLOGY 1985;88:26-34

Severe Idiopathic Constipation Is Associated With a Distinctive Abnormality of the Colonic Myenteric Plexus SHOBA KRISHNAMURTHY, MICHAEL D. SCHUFFLER, CHARLES A. ROHRMANN, and CHARLES E. POPE, II Departments of Medicine and Radiology, the University of Washington School of Medicine, and the Departments of Medicine, the Pacific Medical Center and Veterans Administration Hospital, Seattle, Washington

We analyzed the clinical, radiographic, esophageal manometric, and pathologic features of 26 women with severe, idiopathic constipation. Twenty-four patients were between 19 and 39 yr of age. Stool frequency was once every 5-28 days. On barium enema examination, 9 of 24 patients had colons of increased length and 4 of these 9 patients had colons of increased width (> 1 0 cm). Radionuclide solidmeal gastric-emptying stl.ldies were normal in 23 patients tested. Esophageal manometry demonstrated high-amplitude waves in 10 of 22 patients and long-duration waves in 3 of these 10 patients. Rectal biopsy specimens showed normal submucosal neurons in all patients and melanosis coli in 6. Twelve patients underwent subtotal colectomies for constipation. Conventional light microscopy using hematoxylin and eosin serial sections showed (a) melanosis coli in 4 patients; (b) normal smooth muscle in 11; (c) thinning of the circular muscle in 1; and (d) no apparent abnormalities of the myenteric plexus in any. In contrast, silver stains of the myenteric

Received February 27, 1984. Accepted July 10, 1984. Address requests for reprints to: Shoba Krishnamurthy, M.D. , Pacific Medical Center, 1200-12th Avenue South, Seattle, Washington 98144. This study was supported by grant AM28180 from the National Institutes of Health. Th(l authors thank the following physicians for patient referral : C. Bedard, R. Billingham, R. Carlson, R. Chaffee, K. Curtis, C. Demarest, J. D. Fitterer, W. Friend , D. Gilbert, M. Kramer. S. Lewis. S. Medwell. R. Ogburn. R. Sanford . L. Smith. and J. Wagner. They also thank the Departments of Pathology at the Swedish Hospital and Medical Center. University of Washington. a,nd Pacific Medical Center for helping to make tissue available; Zoe Jonak for superb technical assistance; and Sally VanderZee for manuscript preparation. © 1985 by the American Gastroenterological Association 0016-5085/85/$3 .30

plexus showed (a) quantitatively reduced numbers of argyrophilic neurons in 10 patients; (b) morphologically abnormal argyrophilic neurons in 11; (c) decreased numbers of axons in 11; and (d) increased numbers of variably sized nuclei within ganglia in a1112. A coded analysis of the silver stains of colons from 8 patients with constipation and 19 control cases demonstrated that the pathologic abnormalities of severe idiopathic constipation could be differentiated from controls. Thus, severe idiopathic constipation is associated with a pathologically identifiable abnormality of the myenteric plexus. This abnormality appears different from anything previously described in intestinal pseudoobstruction.

Constipation is a common complaint in medical practice. The vast majority of affected patients either have identifiable reasons for their constipation, or have no evidence of organic disease but can be easily managed with simple measures (1,2). A small, but currently undefined, proportion have constipation that is more severe and persistent, is unresponsive to fiber and mild laxatives, and for which no cause is evident. These patients with "severe idiopathic constipation" often have stool frequencies of less than once per week despite the use of fiber and laxatives. The purpose of this study is to analyze the clinical, radiologic, esophageal manometric, and pathologic features of severe idiopathic constipation.

Materials and Methods We enrolled patients into this study if they had an average of one or less stools per 5 days in the absence of known causes of constipation. Twenty-six such patients were evaluated over a 2-yr period. Twenty-five of 26

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patients were personally interviewed by at least one of the investigators and medical records were reviewed on all. Human Subjects Review Committee approval for this study was obtained on May 13, 1980. Radiographs done at our institution or elsewhere were retrospectively evaluated in 21 of 26 patients. Radiologic reports were obtained in 3 other patients whose radiographs were not available. Radiographic information was unavailable for 2 patients. All evaluations were accomplished without knowledge of the patient's clinical state or history. Plain abdominal films were reviewed for evidence of small or large intestinal dilatation or other abnormalities. Barium contrast examinations of the esophagus, stomach, duodenum, small intestine, and colon were evaluated for evidence of motility disturbance as manifested by delay in transit, retention of contrast material, or retention of gastric or intestinal secretions. Colonic caliber was measured and colonic length was subjectively assessed. The percentage of the abdominal area occupied by the barium-filled colon was approximated by viewing the anteroposterior filled film from the barium enema examination. This "colon to abdomen" ratio provides a means of comparing the colonic size of different patients. Twenty-two patients had esophageal manometry using a low-compliance, perfused catheter system, as previously reported (3). Gastric emptying of solid food was assessed in 23 patients using 600 /-LCi of 99ffiTc-Iabeled sulfur colloid injected into liver pate. The latter was fried and then mixed with beef stew and fed as part of a meal also containing applesauce, whole wheat bread, orange juice, and milk (4). Two rectal biopsy specimens were obtained from all 26 patients using a Rubin tube at 5-6 cm proximal to the anal verge. Sixty serial sections 4 /-Lm thick were cut from each specimen, stained with hematoxylin and eosin (H & E), and examined for the presence of submucosal neurons. Twelve patients subsequently underwent subtotal colectomy with ileorectal or ileosigmoid anastomosis because of the severity of their symptoms and their nonresponsiveness to smooth muscle stimulants and laxatives. The colectomies were performed by nine different surgeons in· five different institutions, usually, but not always, in consultation with the investigators. Six colectomy specimens were personally obtained by one of the investigators, and six specimens were fixed in 10% neutral buffered formalin and forwarded to us from hospitals outside the Seattle area. When specimens were personally obtained, selected areas were fixed in Hollande's solution for conventional light microscopy and in 10% neutral buffered formalin for silver stains. Paraffin blocks of tissue were prepared from the ascending, transverse, descending, and sigmoid colons. For 3 patients who had previous partial colectomies, tissue was not available for the previous resections and only three sites were sampled. Each paraffin block was serially sectioned to obtain 64 sections 4 /-Lm thick. All slides but one were stained with H & E; the last was stained with Masson's trichrome. Each slide was examined by conventional light microscopy. The mean thicknesses of the

MYENTERIC PLEXUS IN CONSTIPATION

27

circular and longitudinal layers of the muscularis propria were measured at three equidistant points along the length of one well-oriented section from each area by using an eyepiece micrometer and averaging the three measurements. The neurons of the myenteric plexus at each sample site were quantified by counting each neuron seen in every eighth serial section of the 64 consecutive sections, as previously described (5). A neuron was counted when its basophilic cytoplasm was identified, even if its nucleus was not seen. Neuronal size was not measured. A mean neuron count of each resected colon was obtained by averaging the counts from all sample sites of that colon. Lorigitudinal sections (50 /-Lm thick) containing myenteric plexus were cut from the formalin-fixed tissue that was immediately adjacent to the four sites sampled above. These 50-/-Lm sections were processed for silver staining by Smith's technique (6). At least five such sections were prepared from each sample site of each colon and reviewed by two of the investigators for the features noted in the next section.

Coded Review A coded review of the silver-stained sections was done by two of the authors (Dr. Schuffler and Dr. Krishnamurthy) using 88 slides from 19 control colons and 54 slides from the first eight colons resected for constipation: three to eight slides were obtained from each control case and six to nine slides from each constipation case. (The four additional colectomy specimens from patients with constipation were obtained after this part of the study was completed and were reviewed in an "unblinded" fashion.) The control colonic tissue was obtained from patients undergoing resections for large polyps or adenocarcinoma and who had no history of chronic constipation. The sites sampled were at least 8 cm from the tumor. All the slides were randomly mixed and no two consecutive slides were from the same patient or control. Our criteria for defining a slide as deriving from a patient with constipation was the presence of (a) a decreased number of argyrophilic neurons and axons and (b) an increased number of nuclei within ganglionic areas. At least one of these criteria, but preferably both, had to be present to make a diagnosis of constipation. The following features were recorded: (a) our subjective impressions of the appearance and number of argyrophilic neurons, argyrophobic neurons, axons, and Schwann cells; (b) the actual number of argyrophilic neurons as quantified per x 40 field in three different ganglionic areas of each slide (done by Dr. Krishnamurthy)-these neurons were identified by their black-staining cytoplasm whereas their nuclei could not be identified by this technique; (c) characterization of any other abnormalities; and (d) final impression, recorded as either control case or constipation. The results of the coded review were analyzed for the following features: (a) total number of slides identified correctly or incorrectly from each control and constipation patient; (b) total number of control and constipation cases identified correctly; (c) reasons for incorrect final impres-

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sions; and (d) number of argyrophilic neurons per X40 field in normal contrbls and in patients with constipation. The slides read incorrectly by each investigator were recoded and reviewed a second time tb analyze whether the reviewers were consist~nt in their interpretation of the individual features listed above. We could then also determine whether the process of learning from our first review translated into a greater accuracy in our second review .

Results Clinical Findings The clinical findings are summarized in Table 1. All 26 patients were women, ranging in age from 19 to 58 yr. The mean age was 31.6 ± 9.2 (mean ± SD) and 24 patients were between 19 and 39 yr of age. The duration of constipation ranged from 6 mo to 30 yr (mean = 13.8 ± 9.7 yr). Although an exact onset of constipai\on was often impossible to identify, 17 patients had a history of constipation for > 10 yr, and 12 were constipated from childhood. Frequency of bowel movements varied from once in 5 days to once in 28 days. Twelve patients had bowel movements once every 5-10 days; 12 others had one movement every 10-20 days; and 2 patients had only oile movement every 21- 28 days. Laxative consumption was common during these times. Twenty-four patients complained of intermittent abdominal discomfort or pain, which sometimes interfered with daily activities. In 19 of 24 patients, the abdominal discomfort or pain was not severe, was relieved by a bowel movement, and recurred -4-7 days later. In 5 of 24 patients, the patients judged the pain to be severe and it was not relieved by a bowel movement. Twenty-five patients complained bf recurrent abdo~inal bloating, and mild distention. All 26 patients complained of malaise and fatigue, which was Table 1. Clinical Features Age: 19-58 yr (24/26:19-39 yr) Sex: Feinales-26, Males-O Duration of constipation: 0.5- 30 yr (17/26: > 10 yr) Stool frequency: once in 5-30 days (16/26: ohce in 10-30 days) Multiple laxatives: 26/26 Metoclopramide: 10/26 Abdominal pain relieved by a bowel movement Abdominal pain not relieved by a bowel movement Abdominal bloating and distention Malaise/fatigue-moderate to severe Malaise/fatigue-----mild Nausea/occasional vomiting Anorexia nervosa in the past Psychiatric illness Dysphagia/chest pain physical examination normal Abdominal distention

19 5 25 15 11 22/4 4 4 2/2 24 2

moderate to severe in 15, and miid in 11. The patients claimed that malaise and fatigue were significantly improved by bowel movements. Twentytwo patients had persistent but mild nausea and 4 of these patients had occasional vomiting. Two patients had dysphagia and chest pain. Four patients had anorexill nervosa diagnosed in the past, which had resolved. On . review cif the records, the diagnostic criteria for anorexia nervosa were not fulfilled and a psychiatrist had not been involved. Four patients had a history of psychiatric illness: 2 had depression, another had a hysterical personality, and the fourth had manic-depressive illness. Only the last patient was on psychotherapeutic drugs [Serentil (Boehringer Ingelheim, Ltd., Ridgefield, Conn.) and lithium]. This patient had a history of constipation since birth, but she had been on these drugs for only the 5 yr prior to evaluation. Six patients had irregular and infrequent menstrual periods. Six patients had undergone abdominal hysterectomies arid 3 of these had had bilateral salpingo-oophorectomies as well. Two patients had undergone left hemicolectomies and 1 patients had undergone a sigmoid colectomy for constipation but without any improvement. One patient had undergone six exploratory laparotomies for diagnosis of abdominal pain with no abnormality detected. No other patient had had an exploratory laparotomy for abdominal pain or suspected bowel obstruction. None of the patients had a family history of constipation or intestinal pseudoobstruction. All patients had had trials of increased dietary bulk (bran or psyllium, or both), but the bulk produced greater bloating and discomfort without increasing stool frequency. The laxatives most commonly used were magnesium citrate, Milk of Magnesia (Ulmer Pharmaceutical Co., Minneapolis, Minn.), Ex-Lax rEx-Lax Pharmaceutical Co., New York, N.Y.), Correctol (Plough, Inc., Memphis, Tenn.), Senokot (The Perdue Frederick Co. , Norwalk, Conn.), Perdiem (William R. Rorer, Inc., Fort Washington, Pa.), Doxidan (Hoechst-Roussel Pharmaceuticals, Inc., Somerville , N.J.), and Dulcolax (Boehringer Ingelheim Ltd., Ridgefield, Conn.) in varying doses. It was difficult to obtain art accurate record of laxative intake; the patients frequently changed preparations and did not take them daily. However, laxative intake could often be as high as 10-15 tablets per day and 1 patient intermittently took up to 30 tablets per day. Ten patients were tried on metoclopramide, 40 mg/day, for at least 2 wk, and 4 patients were tried on neostigmine, 45-90 mg/day, without any benefit. One patient had increased abdominal discomfort while taking neostigmine. Physical examination was entirely normal in 24 patients and only mild abdominal distention was

January 1985

noted in 2. None of the patients was malnourished and none had the impressive amounts of abdominal 'cii;t~Ation often noted in chronic intestinal pseudoobstruction. Twelve patients subsequently had colectomy with ileorectal or ileosigmoid anastomosis because of intractable symptoms interfering with daily life and activities . Their mean age (33.4 ± 11.0 yr) ':md duration of constipation (13.1 ± 8.7 yr) were not significantly different from the nonoperated patients (mean age = 30.1 ± 9.4 yr; duration = 14.3 ± 10.8 yr). All 5 patients with severe abdominal pain and the 2 patients with the least frequent bowel movements (once per 21-28 days) were in the operated group. Three of 4 patients having widened colons on barium enema examination were also in this group.

Radiographic Findings Not all patients had all studies completed; nor could all studies completed be evaluated for each particular finding. Plain abdominal films showed gastric dilatation in 1, small intestinal dilatation in 2, and colonic dilatation in 6 of 18. No other abnormalities were present on the plain films. Barium contrast examinations of the esophagus, stomach, and duodenum in 13 patients demonstrated normal motor function, luminal caliber, and mucosal pattern in all evaluated patients except 1 in whom gastric retention of food material was identified. Small bowel follow-through in 12 patients revealed transit of barium to the cecum delayed be.yond 6 h in 2 patients. Both had normal colonic radiography. In another patient the luminal caliber of the small intestine measured up to 5 cm and the transit time was 5.5 h. The examinations were otherwise unremarkable. Evaluation of the colon in 22 patients was accomplished by either single-contrast or double-contrast (five examinations) technique. Nine of these patients had colons of abnormal length or caliber. Increased colonic length was localized to the transverse colon in 1 patient, affected the sigmoid and transverse colons in 1, and affected the whole colon in 7. Four patients had maximum colonic diameters exceeding 10 cm. Fecal retention or suboptimal preparation was found in 8 of 18 patients and decreased evacuation of contrast material was noted on 5 of 12 examinations. Seven of 18 patients had from onehalf to all of their anteroposterior filled films from their barium enema examinations occupied by the colon. No patient had diverticulosis and 1 had a diminished haustral pattern.

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Esophageal Manometric Findings

Twenty-two of the 26 patients underwent esophageal manometry. All had a normal lower esophageal sphincter pressure (range 15-25 mmHg) and complete sphincter relaxation with swallows. Twelve patients had peristaltic waves of normal amplitude and duration. Ten patients, however, had high-amplitude (180-240 mmHg) peristaltic waves and, of these, 3 had long-duration waves (>8 s). No patient had spontaneous or simultaneous contractions. Of the 2 patients who complained of dysphagia and chest pain, 1 had a normal manometry whereas the other had high-amplitude peristaltic waves . Gastric-Emptying Studies Of the 23 patients tested, all had normal gastric emptying (normal t1/2 of 120 ± 32 min for a 900-g meal). The 23 patients tested included the 2 patients who had delayed transit of barium to the cecum and the 1 with retained gastric secretions. Pathologic Findings

Conventional light microscopy. Rectal biopsy specimens in the 26 patients showed normal mucosa except in 6 patients who had melanosis coli. Submucosal ganglion cells of normal appearance were present in all patients. Conventional light microscopy of the 12 resected colons showed (a) melanosis coli in 4 patients; (b) normal circular muscle layer thickness in 11 of 12 patients; (c) thinning of the circular muscle in 1 of 12 patients (circular muscle thickness 386.8 /Lm; normal 1031 ± 262 /Lm; 95% lower confidence limit 579 /Lm); (d) normal longitudinal muscle thickness in 12 of 12 patients; (e) no evidence of abnormal fibrosis or degenerative changes in the muscle layers of any of the 12 patients; and (f) no inflammatory cells within the myenteric plexus. Mean neuron counts within the myenteric plexus were normal in 11 patients, varying from 24.5 to 65 .1 neurons per section per 100-mm length of smooth muscle (normal 54.6 ± 19.2). The mean count in 1 patient (the same patient with the thin circular muscle) was slightly low at 20.3 neurons per section per 100-mm length of smooth muscle (95% lower confidence limit 22). Silver stains. In contrast to the conventional histology, the silver stains demonstrated distinctive abnormalities of the myenteric plexus. (a) Ten of the 12 patients had decreased numbers of argyrophilic neurons (Figure 1). In 11 patients, those argyrophilic neurons present ranged in appearance from normal to very abnormal (Figure 2). The abnormal neurons were small, shriveled, or slightly

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Figure 1. A. Ganglionic area from a control colon showing plentiful normal argyrophilic neurons with multiple nerve processes and nerve fib ers. B. Ganglionic area of colon from a patient with constipation showing lack of argyrophilic neurons, paucity of nerve fibers, and presence of multiple nuclei. The arrows denote muscle fibers. (Silver, both x 166; scale bar = 50 ""m.)

swollen, and had uneven staining and decreased stain uptake. Neuronal processes ranged from decreased in number to absent and, when present, were usually smaller than normal in size. Large multipolar neurons were almost never seen. Only 1 of 12 patients had entirely normal argyrophilic neurons. (b) There were decreased numbers ofaxons within the nerve tracts between ganglia in 11 of 12 patients (Figure 3). This was patchy in occurrence and tended to vary with the presence or absence of argyrophilic neurons, i.e., axons were more common in tracts connected with ganglia having larger numbers of

GASTROENTEROLOGY Vol. 88, No.1, Part 1

argyrophilic neurons. Five patients had very minimal axon fragmentation, but this was not significant because it was no different than the slight amounts of apparent axon fragmentation seen in the control slides . (c) Schwann cell nuclei were usually not distinct or prominent within the nerve tracts. However, some Schwann cell nuclei were visible in 7 patients, although this finding was present in relatively few areas. No patient had Schwann cell hyperplasia. (d) No definite abnormalities of argyrophobic neurons were identified. However, these neurons could not always be identified with confidence because of the presence of clusters of nuclei in the ganglia, which tended to obscure any cells that were not clearly argyrophilic. (e) There were increased numbers of variably sized nuclei with active-appearing chromatin in the ganglia of all 12 patients (Figures 1 and 2). These nuclei were often present in distinctive clusters and some of the nuclei had associated faintly staining cytoplasm, which identified such nuclei as belonging to argyrophobic neurons. The cytoplasm belonging to the other nuclei was not visible so that the origin of these nuclei is indeterminate. This finding could also be patchy in occurrence . It was the only abnormality of the plexus identified in the 1 patient having a normal number of argyrophilic neurons (Figure 1B). (f) Inflammatory cells were never seen in any of the patients' myenteric plexuses. The above abnormalities were usually present in all areas of the colon, although they tended to be less pronounced in the ascending colon. However, the abnormalities could be patchy in distribution and vary from present to absent between areas , between slides prepared from a single area, and between ganglia present on a single slide. Coded Review In our initial review, reviewer No.1 identified 80/88 (91 %) of control slides and 43/54 (80%) constipation slides correctly. Reviewer No. 2 identified 83/88 (94%) of control slides and 41/54 (76%) constipation slides correctly. When the data were analyzed to determine the number of patients and controls identified correctly, both reviewers identified 18/19 controls and 7/8 constipation patients. A control case was considered to be incorrectly interpreted if more than one slide was interpreted as being from a patient with constipation. A constipation case was considered to be interpreted incorrectly if >50% of the slides were interpreted as being from a control case. Thus, only 1 control case was interpreted as "constipation" and 1 constipation case as "control."

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Figure 2. A. Ganglionic area from control colon illustrated in Figure 1, showing normal argyrophilic neurons and processes, and nerve fibers. B. Ganglionic area of colon from case 3 with constipation. It shows argyrophilic neurons and nerve fibers, but with an increased number of nuclei, some of which have associated cytoplasm , identifying them as argyrophobic neurons (arrows). C. Ganglionic area from case 8 with constipation. One small argyrophilic neuron with only one process is seen (arrow) within a background of numerous nuclei. D. Ganglionic area from case 9 with constipation, showing only one argyrophilic neuron (arrow) and numerous nuclei. (Silver, all x 419 ; scale bar = 25 /-Lm .)

Of the total of 284 slides read by both reviewers, 33 were read as the incorrect diagnosis by either or both reviewers on the first review. On the second review, reviewer No. 1 identified all 19 control patients and 7 of the 8 constipation cases. Reviewer No.2 identified 18 of the 19 control patients, but all 8 of the constipation patients. Among the 8 patients with constipation, 6 had a preponderant number of slides identified correctly as deriving from patients with constipation (Table 2). Of the other 2 patients, 1 had 7 of 12 slides identified as constipation whereas the other had 7 of 12 slides identified as control. On reviewing the former case in an unblinded fashion, we determined that, indeed, there were areas on the five slides read as control that were normal in appearance. This patient, therefore, had patchy abnormalities. The second case, however, was misidentified by the first reviewer on all six slides. This patient had a normal

number of argyrophilic and argyrophobic neurons and axons. The only abnormality present was an increased number of nuclei within the areas of the ganglia (Figure 2B). It is clear, therefore, that with few exceptions, the histology of patients with severe idiopathic constipation can be differentiated from controls. It is also of interest to note the interobservor variation. The two reviewers agreed on 120/142 slides or 84% of the first review and on 131/142 slides, or 92%, as a result of the second review. Table 3 shows the neuron counts for each of the 8 patients in the coded review as well as for the 4 other constipated patients whose argyrophilic neurons were quantified in an "unblinded" fashion. As a group, the constipated patients had about half the number of argyrophilic neurons as the controls, and 10 of 12 constipated patients had argyrophilic neuron counts that were below the 95% confidence limit

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of the controls. Thus, a significantly reduced number of argyrophilic neurons is a common feature of severe idiopathic constipation.

Discussion It is not widely appreciated that severe, idiopathic constipation is a distinct clinical syndrome (1,7-11). It is likely that many patients have been inappropriately designated as having "catharticabuse colon," "psychogenic constipation," or "irritable bowel syndrome." Our study suggests that not only is severe idiopathic constipation a distinct disorder, but that it is associated with an identifiable, pathologic abnormality of the colonic myenteric plexus. As we began this study, we theorized that severe idiopathic constipation could be caused by abnormalities of the colonic smooth muscle, the myenteric plexus, or both. We found no abnormalities of the smooth muscle except for thinning of the circular muscle in 1 patient. In addition, conventional H & E staining revealed no abnormalities of the myenteric plexus, and the mean neuron counts were normal except in 1 patient who had slightly reduced counts. However, this method has serious limitations in demonstrating abnormalities of the myenteric plexus. We were not surprised, therefore, to find abnormalities of the myenteric plexus by Smith's silver method. The abnormalities were different from those previously reported in several pseudoobstruction syndromes (5,6,12,13). Our coded review and analysis of the silver stains demonstrated that the constipation cases could be differentiated from controls and that a distinctive pattern of abnormality was usually present, consisting of (a) decreased argyrophilic neurons; (b) decreased neuronal processes (dendrites and axons); and (c) clusters of variably sized nuclei in the ganglia, with some being associated with faintly staining cytoplasm. What is the possible explanation for this pathology? Although we are uncertain, we theorize that the increased nuclei may represent immature neurons, the cytoplasm and processes of which have not acquired argyrophilia and are, therefore, not visible (13). The lack of argyrophilic neurons would also explain the decreased numbers of visible nerve fibers. The fact that the neuron counts were normal by H & E staining suggests a qualitative defect of neu-

Figure 3. A. Nerve tract with numerous axons from a control colon. B. Nerve tract from case 8 with constipation showing only one darkly stained axon above (arrow) and one below, and a background of Schwann cell nuclei. C. Nerve tract from case 9 with constipation showing just a few dark-staining axons. (Silver, all x419; scale bar = 25 !Lm.)

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Table 2. Silver Stains (Coded Review)

•

Control cases (n = 19) Constipation cases (n = 8) Individuals with constipation No.1 No.2 No.3 No.4 No.5 No.6 No.7 No.8 o

Interpreted as constipation

Slides o (n)

Interpreted as control (n)

176 108

171 19

5 89

14

0 3 7 0 5 2 2 0

14 9 5 12 7 10 16 16

12 12 12 12 12 18 16

(u)

Pooled slides from both reviewers, as result of the two reviews.

rons that can only be appreciated by the silver staining method. We have seen similar clusters of nuclei along with decreased numbers of argyrophilic neurons in infants with pseudoobstruction (unpublished observations). It is also possible that neurons that were previously argyrophilic underwent some type of injury which caused a shift to argyrophobia, and that some of the nuclei represent Schwann cells. Further studies using transmission electron microscopy are being done to enhance our understanding of these changes. Although the exact functional significance of argyrophilia is unknown, it would appear that the absence of argyrophilia is associated with definite iIIlpairment of function. Although there are several reports of colonic resection for idiopathic constipation, histopathologic abnormalities were noted in only three (7,11,14). The first reported hypertrophy of the colonic muscle layers (14). The second reported a granuloma in the myenteric plexus of 1 patient, and hyperganglionosis, patchy disappearance of neurons with inflammation of the plexus, and Schwann cell hyperplasia in 3 differElnt patients (11). The third used silver staining to define abnormalities of the myenteric plexus in 4 patients, consisting of decreased argyrophilic neurons and processes, absence of Schwann cell hyperplasia, and presence of many neuroblasts in 1 patient (7). The findings of this third study are consistent with ours, whereas the findings of the other two are not. Could the pathologic abnormalities that we report have been induced by laxatives? Against this hypothesis are the facts that (a) all out patients were severely constipated before they began to take laxatives; (b) many of our patients were taking laxatives intermittently; (c) only 23% had melanosis coli, a marker of excessive anthraquinone intake; and (d) 1 patient who had had a colonie resection was 21 yr old and had been on small doses of laxatives for only

33

2 yr. Furthermore, the pathology does not appear to be destructive in nature. There was no frank axon degeneration, no Schwann cell hyperplasia in nerve tracts, and no inflammatory reaction. Even though several reports suggest that laxative abuse causes a "cathartic colon," the patients reported are. very poorly defined and there is no conclusive evidence in humans that laxatives cause damage to the myenteric plexus (15-24). Is severe idiopathic constipation not just another manifestation of chronic idiopathic intestinal pseudoobstruction? Like chronic idiopathic intestinal pseudoobstruction, severe idiopathic constipation is characterized by severe motor dysfunction, identifiable pathology within the neuromuscular apparatus of the bowel, and esophageal involvement in many cases (25). In contrast to chronic idiopathic intestinal pseudoobstruction, however, the patients do not present with a clinical picture mimicking bowel obstruction; plain films of the abdomen do not usually show a pattern of ileus or air-fluid levels; the small bowel is usually not involved, at least by radiography; and the esophageal manometric pattern is one of "supersqueeze" or "nutcracker esophagus" rather than aperistalsis. Thus, severe idiopathic constipation is a related, but somewhat dissimilar, syndrome. We are uncertain as to the distribution of the pathologic abnormalities of severe idiopathic constipation along the entire gastrointestinal tract. Perhaps gastroduodenal and sman bowel manometry and pathologic studies of the small bowel will help to identify whether small bowel involvement is present in some of these patients as we have reason to

Table 3. Silver Stains Mean no. of argyrophilic neurons/ x40 ganglionic field Coded Review Control cases (n = 19) Constipation cases (n = Il) Individuals with constipation No.1 No.2 No.3 No.4 No.5 No.6 No.7 No.8

14 ± 2.7 7 ± 4.0 0 4.4 b

6.8 b 14.3 b

6.0 b 4.5 b 12.0 4.8 b 3.4 b

Uncoded Review No.9 No. 10 No. 11 No. 12 p < 0.01 compared with control cases. limit of controls.

o

b

Below 95% confidence

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KRISHNAMURTHY ET AL.

suspect. Although gastric involvement seems to be uncommon in our patient population, just under 50% of our patients did have esophageal involvement with manometric findings consistent with a "nutcracker esophagus." This finding suggests that the esophageal myenteric plexus might be involved. All of our 26 patients were relatively young women. In large surveys done to assess stool frequency, women complain of constipation more often than men and tend to have lower stool frequencies. Constipation is also common in pregnancy. However, it is doubtful that these factors help to explain the absence of males in such a severely constipated group. In contrast to chronic idiopathic intestinal pseudoobstruction, in which approximately onethird of cases are easily identified as familial, none of our 26 patients had familial involvement. A genetic defect is still possible, however, because there are precedents for genetic disorders occurring solely in females. Aicardi's syndrome, incontinentia pigmenti, and Rett's syndrome are all examples of such disorders (26-29). In conclusion, we have identified a group of young women with severe constipation who have significant clinical disability. Some of these patients have a distinctive abnormality of the myenteric plexus which is different from the abnormalities described in chronic idiopathic intestinal pseudoobstruction and which can be easily differentiated from controls. We hypothesize that these abnormalities may be developmental in origin and may involve areas of the gastrointestinal tract other than the colon. These hypotheses remain to be proven by additional studies and longer follow-up.

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